The importance of critical analysis of treatment methods and results in cancer is paramount and the development of controlled clinical trials to assess these parameters is receiving increasing national attention. In view of the difficulty of maintaining such trials within single institutions because of the necessary limitations of patent material, the Radiation Therapy Oncology Group has been formed to enable various institutions to cooperate in this way and pool their material. With the larger number of patients available for study, various pertinent questions in the management of cancer by means of radiation therapy with or without chemotherapy and surgery are being investigated. Treatment protocols are under constant professional analysis by the Biostatistical Center of the Group and the quality of radiation therapy maintained by strict supervision from the Radiologic Physics Center. Additional information to be obtained by the Group will include long term analysis of the complications of radiation and as an informative source for collecting the result of radiation therapy in rare tumors and techniques. To date this Department has been entering cases for study as a Provisional Member, but has now been elected to full Membership.